How to maintain expand/collapsed state of rows during page refresh in Javascript TreeGrid?

var currentData = []
var treeGridObj = new ej.treegrid.TreeGrid({
dataSource: sampleData,
childMapping: 'subtasks',
height: 350,
treeColumnIndex: 1,
allowPaging: true,
dataBound: dataBound,
collapsed: collapsed,
expanded: expanded,
columns: [
   {
    field: 'taskID',
    isPrimaryKey: true,
    headerText: 'Task ID',
    width: 70,
    textAlign: 'Right',
   },
   {
    field: 'taskName',
    headerText: 'Task Name',
    width: 200,
    textAlign: 'Left',
   },
   {
    field: 'startDate',
    headerText: 'Start Date',
    width: 90,
    textAlign: 'Right',
    type: 'date',
    format: 'yMd',
   },
   {
    field: 'endDate',
    headerText: 'End Date',
    width: 90,
    textAlign: 'Right',
    type: 'date',
    format: 'yMd',
   },
   {
    field: 'duration',
    headerText: 'Duration',
    width: 80,
    textAlign: 'Right',
   },
   {
    field: 'progress',
    headerText: 'Progress',
    width: 80,
    textAlign: 'Right',
   },
   { 
    field: 'priority', headerText: 'Priority', width: 90 },
   ],
  });
  treeGridObj.appendTo('#TreeGrid');
 
  function collapsed(args) {
    currentData.push(args.data);
    store(args);
    //storing collapsed record in local storage using setItem method
  }
  function expanded(args) {
    currentData.push(args.data);
    this.store(args);
    //storing collapsed record in local storage using setItem method
  }
  function store(args) {
    currentData.push(...treeGridObj.getCurrentViewRecords().
    filter((i) =>    i.hasChildRecords).filter((i) => !i.expanded));
    this.currentData = Array.from(new Set(this.currentData));
    window.localStorage.setItem('currentData', JSON.stringify(currentData));
  }
  function dataBound(args) {
    if (treeGridObj.initialRender) {
      //checking whether it is initial rendering
      var data = JSON.parse(window.localStorage.getItem('currentData'));
      //retriving collapsed record in local storage using getItem method
      if (data) { 
        var completeData = treeGridObj.grid.dataSource;
        var primaryKeyFieldName = treeGridObj.getPrimaryKeyFieldNames()[0];
        for (var i = 0; i < data.length; i++) {
          var value = [];
          for (var j = 0; j < completeData.length; j++) {
            if (completeData[j][primaryKeyFieldName] == data[i][primaryKeyFieldName]) {
              value = completeData[j];
            }
          }
          treeGridObj.collapseRow(null, value); //collapsing row using collapseRow           
        }
        currentData = [];
        window.localStorage.setItem('currentData', JSON.stringify(currentData));
      }
    }
  }